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About decoyp

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    Star Forming

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    Spalding Lincolnshire
  1. I'll try and re-align both lenses to be pointing at the same thing initially. Probably do this on something unmistakable like Jupiter just so I know both are looking at the same thing. Then I'll try again. I'm sure that as you say PA is an issue and I am going to go down the EQmod route ASAP and use Alignmaster which I've seen the youtube video of and it looks great. I've heard of people using PHD to drift align but I tried it and just got confused about which way to alter the mount, and ended up with a pretty trashy PA. Anyway I dont't get that much time at the scope and we don't have enough clear nights to waste messing around with PA so I want a nice easy solution. Thanks for all your help. BTW what exactly is "Cone Error" Cheers Richard
  2. I think that the FOV of the guide scope could be on the edge of the imaging FOV. It was just a rough test and I foolishly did not consider whether this would be an issue. I suppose it could be cone error I'd know better if I actually knew what cone error was :-) Seriously though I can guess what it is from what's being said here. The two scopes are not particularly aligned - both are mounted on an aluminium plate and I have purposely made them so I can move the guide scope to align to a guide star if necessary. How aligned do they have to be ?? I'm probably within a few degrees (I mean they are not 90 degrees to each other or anything daft like that) .
  3. Right. I had another go at this last night and tried tweaking some values in PHD to get the graph a bit flatter. Still not great but it has improved, however I have noticed something else and have been thinking about my setup. TRhe followwing questions have occured to me ...... 1- My test shots show star trailing but only in the leftmost part of the frame. The stars in the right hand side of the frame appear to be significantly better shaped. 2- I am using a DSLR with a 135mm prime focus tele. My guide scope however is a QHY5 with a 400mm tele lense attached. Quite a big difference. 3- Is the difference I am seeing in star shape across the frame due to field rotation because my polar alignment isnt as good as I'd hope? 4- Could the above in point 3 be partly due to the difference in ratio of the scopes and the fact that I can't be certain the guide scope is looking at exactly the same piece of sky as the camera? Any help much appreciated. Thanks Richard.
  4. Sorry, I've been at work and haven't had chance to reply to any posts. I was wondering whether to try another guiding program too. Might do that soon just to see what happens. I will also check the balancing to see if that has an effect. I must admit though I've been reading about Alignmaster and EQmod and am tempted to bite the bullet and go down this route. At least I'll be certain that my polar alignment is spot on - that would take one variable out of the equation. I know it doesnt help, but I'm glad I,m not the only one having problems like this.
  5. Hi. I've just finished building a ROR observatory and have had to reset my mount on the pier because I had to raise the whole thing by about 10 inches (long story). I've done a re-alignment by drift aligning which I think is OK. There was pretty much no movement after about 10 mins. I'm also using PHD to guide. However I have taken a few test shots wide field just to check things are OK and I've noticed trailing on all the shots. The PHD graph is also not very flat (no screen grabs I'm afraid). The RA (blue trace) seems to oscillate either side of the horizontal graph line by one whole division up or down from the middle horizontal line. This oscillation is in phase with each exposure taken from the QHY5 camera i.e about every 2 seconds. DEC trace seems to come into the graph from the top left hand corner and then steadily descend to the horizontal axis and then flatten out. Can anyone shed any light on this? should I be adjusting some of the brain settings or biasing the counterweights somehow ? Any help greatly appreciated. Why does this always happen when we get a plague of clear skies !!!! Thanks Richard
  6. Here's some more details of bits etc as requested : - Tha castors were from BIL castors online Type BZA75PL - Bearing type: Plain bore - Fixing type: Plate - Swivel or Fixed: Fixed - Wheel Types: Black polypropylene They were only a couple of pounds each as I remember. I got the 75mm dia ones to make sure the central boss cleared the unistrut. I did have to modify the width to ensure they fitted into the channel with some clearence and were free running. If you've got access to a lathe this mod would be easy, if not it's a bit fiddly. I had to modify mine using a drill in a drill stand and clamping a cutting tool to the drill table. By lowering the rotating wheel onto the tool, you can shave bits off gradually. Kind of like a vertical lathe but much more dangerous !! That was the main problem I had with using unistrut - I couldn't seem to find a castor that would fit and be a large enough diameter. I mentioned that I have found a supplier for leadscrew and leadscrew nuts. I have included a link to this supplier. I must stress I haven't bought these bits yet so I don,t know what the supplier is like. But on the face of it, these components look like the kind of thing I will use. I intend to design a drive plate that will hold the leadscrew nut and fix to the roof threreby moving the roof when the screw rotates. I have made several bits from plate aluminium for my pier and associated mountings so this is my material of choice for the drive plate. I have found that plate aluminium can be cut fairly easily using a jig saw with a metal cutting blade. You have to set the saw on a slow speed and use plenty of oil (wd40 or similar). Using this method I have managed to cut plate 12mm thick. There is a fair bit of work to do with a file afterwards though !! You can buy aluminium plate online too - I get most of mine from e-bay. Here's the link for the screw bits :- WMH Transmissions Ltd - Product List - SIZE 20MM X 4P R.H. Having looked again I'm not sure it is an acme thread - but I suppose for my purposes it doesn't matter. Richard
  7. I take your point about water collecting in the runners David. I was thinking as I did it there may be a problem and that I perhaps should have used slotted Unistrut instead to shed water. I could still put a few holes in the sides of the rails to provide some drainage so I might do that yet. The problem of snow had also occurred to me but I resolved to just making sure I cleared it off by hand when necessary. I must admit I never thought of inverting the mechanism so the rails were on the roof instead - good idea - too late now!! Good point also about making sure the roof is retained in high winds. I will be fitting a retaining latch system to the roof to hold it down when in the closed position. This also will give security against anyone gaining access by simply sliding the roof off. I need to do this soon before fitting all my gear in it. I'm not too fussed about roof retention in the open position as I do not intend to be using the observatory in high winds and it is heavy enough to stay in place under normal conditions. (Famous last words). I am fairly sure my roof will be automated by using a kind of leadscrew and carrier method. I've looked at other options including garage door openers and have decided that this method will suite my design best - but there is time to change my mind yet. I've found a supplier that sells leadscrews (20mm acme thread 2m long) and leadscrew nuts at a reasonable price. This method will package neatly down one side of the shed and will give plenty of mechanical advantage even using a fairly modest dc motor.
  8. Thanks guys. Will post some more pics when its fully fitted out. May be a while before I get it automated but watch this space.
  9. Hi to anyone who is interested !! I guess if you're looking at this forum you must be. I've attached some pics of my almost completed Observatory. I bought the shed cheaply from Focus just before it shut down. I have made some fairly major strengthening mods to it, as well as the roof modification obviously. The floor is a suspended decking area constructed to the right dimensions for the shed to sit on. I also constructed a 4x2 timber frame for the shed to effectively bolt to which incorporated all the roll off structure that would be required etc. It would probably have worked out cheaper to build the whole thing from scratch though I have re-used a lot of original shed material. Last year I built a pier for my HEQ5 mount and have pretty much just built the shed around it. The roof runs on eight castors and the rails are made from galvanised channel. I got the channel from a local electrical wholesaler. Its called Unistrut , and is used extensively in industrial electrical installations for hanging cable tray etc. I thought it was perfect for the job. I had to modify the castors to fit into the channel though. I also ended up building the shed a bit higher than previously intended as the original height only just cleared the scope and I wanted to future proof it for when I beg my wife to allow me to buy another (not another one !! ) scope. As a result I have had to make an extension piece to extend the pier by about 10 inches (not shown here). I'm still half way through making this bit. There's still some sealing work to do around the bottom of the shed sides where it meets the base. Also I want to line it with plywood at some point. I also need a table for the PC etc. I intend to automate the roof at some point in the future and am hatching a plan to do this !! Thanks for looking. Any comments/ suggestions welcome. Richard
  10. Sounds like just the job. I didn't mean to come across as telling people how they should do stuff. It's just that when mine went into melt down, it was a bit of a shock and I wanted to share the experience so that it didn't happen to someone else. Mind you, it was a probably a bit stupid using a car battery to power it - I should have known better. Seemed like a good idea at the time. Never mind. As they say "what doesn't burn your house down makes you stronger" or something like that !! Cheers Richard
  11. Just read Astroblaggers thread about home made dew heaters. I just thought I should mention from my own experience, the importance of incorporating a suitably rated fuse in the dew heater circuit. The one that Astroblagger has illustrated does not seem to have one. I made one of these dew heaters using exactly the same method (got the idea from IceInSpace as someone also pointed out). It worked great until one night when I was packing away the gear the dew heater leads shorted out. I was powering it off a car battery. The leads (speaker cable 1mm2) just melted in a matter of seconds. I was very lucky not to end up with melted PVC all over the OTA. It could also start a fire in a wooden observatory quite easily which would be much more serious and expensive. I still use the same design of dew heater but have incorporated an in line fuse in the lead. You can buy them from maplin or RS. The rating of the fuse will depend on what size heater you are using. Make sure your cable is big enough to take the current and that your fuse is rated properly to prevent disaster in case of a short circuit. Don't get caught out like I did. All the best Richard
  12. Thanks Tony. I'll probably be picking your brains a bit later about these ideas if that's OK. Cheers Richard
  13. Wow Tony. you built your own CNC machine !! I'm sure a RoR observatory is really no challenge for you. Can you let me know what controllers you used for the stepper motors and the motor spec etc. I'm very interested in this as it is for me the best solution, because it lends itself to computer control. I don't want to really get into observatory control software as it probably does a lot more than I need at the moment. However a basic open/close computer interface and someone to write me a very basic application is probably not outside the realms of possibility. I was going to do it the old fashioned way with relays, DPDT switches etc but always wanted to get computer control ultimately. I'm coming around to the threaded rod idea too. I have given it some thought and there are several configurations that would suit my setup. Great suggestion Gina about one drive shaft at the rear providing drive to both sides of the roof. That is worth developing too. Having a central drive will not work for me as it would get in the way of my scope setup, and could block a clear view in some orientations it would probably be fine for some designs though. Thanks for all the suggestions. Will keep you posted on the progress and some pics at some point. I wont get to work on it until the weekend now as the evenings are too dark. Hopefully I can get the roof completed and then I've broken the back of it from the construction point of view. Should be up and running in manual mode before long. Thanks Richard
  14. I like the sound of all these ideas. The gate opener sounds like it would give a professional solution but also sounds a bit too dear for me. I hear what you're saying about reaching a point where you can't be bothered about doing it yourself. We all reach that point at different times I guess. The threaded rod idea sounds great also. That would give quite a controlled motion with no chance of the drive jumping out of engagement if there is any flexibility in the system. Perhaps a type of universal joint that could be uncoupled when needed could be used to allow manual operation. I don't know if you've already got this built in. The pulley system also sounds like a good solution. One question has occurred to me though. If the drive system is only on one side of the roof (I presume these ideas are not installed down the middle of the shed), will that put a twist on the roof as it tries to open ? I was envisaging putting a motor on each side to reduce the load and avoid twist. Although they would have to be in sync or it might cause other problems. I just put a set of scales against the roof and pushed on it to see how much force it takes to open it. It registered about 3Kg to start and about 2.5Kg when running. Didn't seem too bad although the roof felt isn't on yet so it will probably increase. I'll have to dig around on the web to see how you equate this to "torque required" and build in a factor of safety before I start looking for motors. It seems that the car industry has the answer though in the form of window motors/ starter motors etc.
  15. Thanks for the replies guys. Seems that most people have similar ideas and consequently we are facing the same stumbling blocks and financial constraints. The problem is for me not really knowing how much load its going to take to actually start the roof in motion. I've got the roof almost completed on my shed and it seems to move quite easily but the initial starting effort is quite high. Suppose I could get one of those spring gauges we used to use in physics at school for measuring load in Newtons (more years ago than I care to remember !!), and then I would at least know a figure to base a design around. I'm not too concerned about motors running on a bit as I think this could be controlled with a carefully placed limit switch and some kind of damper. I've seen hydraulic dampers on ebay. You are right Gina. The kind of motor choice is critical. And the fact that they all reverse in slightly different ways. I'm hoping to achieve this in the old fashioned way using relays and avoiding expensive custom built motor controllers. Unless anyone knows of a cheap off the shelf solution. I've already woken up in a cold sweat trying to figure out the exact configuration of the relays to achieve this. I too initially thought of a garage door opener, but the problem is packaging into my design. My roof rolls off onto a gazebo type structure. The door opener would have to sit there somewhere and be open to the elements. Also on the ones I've seen, they can be energised by pushing a button on the side, not so secure with all that gear inside the shed. Housing the opener inside the Observatory would probably take up too much room. However the jury is still out on that idea as it has the merit of being an off the shelf solution. I will take some pics of my setup soon and post them. Cheers richard
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